Gases containing pollutants, such as sulfur dioxide, are produced in many industrial processes. For example, industrial boilers, calciners, smelters, and bake furnaces, to name a few, may produce gas streams containing sulfur dioxide. The United States Environmental Protection Agency (“EPA”) regulates sulfur dioxide air pollution in the United States. More specifically, the EPA sets air quality standards regarding sulfur dioxide (40 CFR §§50, 53, and 58). Compliance with these (and other) EPA air quality standards may require removal of at least some sulfur dioxide from a gas stream.